Compact speed sensitive timing device for internal combustion engines



Sept. 17, 1968 .1. M. BAILEY 3, 0

COMPACT SPEED SENSITIVE TIMING DEVICE FOR INTERNAL COMBUSTION ENGINESFiled Sept. 12, 1966 R r" 8 I7 I W El .1 5 44 Z7\ 39 4 5z\ 43 20 24 i:48 A INVENTOR. JOHN M. BAILEY ATTORNEYS 3,401,572 Patented Sept. 17,1968 United States Patent Office 3,401,572 COMPACT SPEED SENSITIVETIMING DEVICE FOR INTERNAL COMBUSTION ENGINES John M. Bailey, EastPeoria, Ill., assignor to Caterpillar Tractor Co., Peoria, Ill., acorporation of California Filed Sept. 12, 1966, Ser. No. 578,783 6Claims. (Cl. 74395) ABSTRACT OF THE DISCLOSURE Compact mechanism foradjusting engine timing has a fluid filled vortex chamber containedwithin a cam shaft drive gear and centrifugally generating a forceproportional to engine speed. Means translate the force into axialmovement at a helical spline coupling between the gear and one of therotating members engaged therewith to vary the annular phaserelationship therebetween in accordance with engine speed.

This invention relates to internal combustion engines and moreparticularly to mechanisms for automatically adjusting the timing offuel injection or ignition in response to changes in engine speed.

In a typical internal combustion engine, the fuel injection or ignitionmechanism is coupled to the engine crankshaft through a system of gearsand cams or equivalent means. Thus, in the absence of suitableadjustment means, the timing of fuel combustion relative to pistonposition is fixed by the design parameters of the engine. However suchengines operate much more efficiently if timing is varied with changesin engine speed. Timing should be advanced as engine speed increases andretarded with decreases in speed and it is preferable that the means formaking this adjustment operate automatically.

A form of automatic timing adjustment mechanism which is extensivelyused on diesel engines for example, senses changes in engine speed bymeans of a roating shaft coupled to the engine crankshaft and carryingflyweights which move radially in response to changes in the speedthereof. The flyweights control the axial position of a rotating elementof the fuel injection pump drive. The drive element has helical gearteeth or a helical spline mounting so that the axial movements of theelement advance or retard timing according to the direction of themovement.

Flyweight controlled systems of the type discussed above are somewhatbulky and complex and are subject to rapid wear, particularly around theflyweight pivots, which interferes with eflicient operation andaggravates maintenance. To avoid these problems a second class of timingdevice is sometimes used in which engine speed is sensed through thepressure of the engine lubricating oil or the engine fuel oil. As thepumps which generate such pressure are also operated by the engine crankshaft, the oil pressure is a function of engine speed. Typically, theoil pressure is caused to control the axial position of a helicalcomponent of the fuel injection drive and thereby adjust timing asdiscussed above with reference to fly weight controlled mechanisms.

As heretofore constructed, oil pressure controlled timing devices havestill been more bulky and complex than is desirable and have beensubject to certain operational difficulties peculiar to such mechanisms.Such timing devices have been very dependent, for example, on precisefunctioning of the oil circulating pumps and can be strongly influencedby pump wear, changes in oil viscosity and other factors. Further, manytiming devices of this class are limited to use with either distributorfuel injection systems or in line fuel pumps but are not adaptable toboth. 1

The present invention provides a timing mechanism which is oilcontrolled in a unique manner that removes the disadvantages of prioroil pressure operated devices and obtains the advantages of flyweightsystems in a very compact and low maintenance mechanism. In particular,the timing is not controlled by the engine oil pressure per se as inprior devices but is determined by a volume of oil which rotates withinmeans coupled to the engine crankshaft. Thus an oil pressureproportional to engine speed is self generated within the timingmechanism itself by centrifugal force and is not severly affected by thecondition of the remote oil circulating pump or other extraneousfactors. The mechanism requires only a small number of parts which canbe largely contained within the drive gear and drive shaft of the fuelinjection system so that extreme compactness results. 1

Accordingly it is an object of this invention to provide an automatictiming adjustment mechanism for internal combustion engines which hasrelatively few parts, is extremely compact and requires littlemaintenance.

It is another object of this invention to provide an engine timingdevice operated by an oil pressure proportional to engine speed which isless dependent on the condition of remote oil pumps, oil viscosity, orother extraneous factors.

It is still another object of the invention to provide automatic timingadjustment means for an engine which may be largely contained within thefuel injection system drive gear and drive shaft.

It is a further object of the invention to provide a compact speedsensitive timing adjustment mechanism for engines that is adaptable foruse with both distributor type and in line type fuel injection systems.

It is still a further object of the invention to provide an enginetiming adjustment mechanism which is relatively free from wear pronemechanical parts and which is inherently damped to avoid hunting aboutan optimum timing adjustment.

The invention, together with further objects and advantages thereof,will best be understood by reference to the following specificationtogether with the accompanying drawing, of which:

FIGURE 1 is a section view showing a fuel injection pump and drive shaftand drive gear of the fuel injection system of a diesel engine with thepresent invention embodied therein; and

, FIGURE 2 is a section view of portions of the drive train of a dieselfuel injection system utilizing a second embodiment of the invention.

Referring now to the drawing and more particularly to FIGURE 1 thereof,a diesel fuel injection pump 11 is usually operated by a rotating camshaft 12 having integral cams 13g thereon which translate a cam follower14 associated with each injection pump, the detailed construction andoperation of such pumps being well understood within the art. Camshaft12 has a drive gear 16 at one end which is engaged by another gear 17.Gear 17 is a component of the engine drive train, coupled directly orindirectly to the engine crankshaft, so that the timing of operation ofthe fuel injection pump 11 is thereby related to the movement of theassociated engine pistons.

Drive gear 16 and gear 17 are enclosed by a housing 18 having an adaptersection 19 with a bore 20 through which the end of camshaft 12 extendsto receive the drive gear.

As hereinbefore discussed, optimum engine performance requires that thetiming of fuel injection relative to piston movement be advanced asengine speed increases and retarded as speed decreases. Automaticmechanism for this purpose is contained within the drive gear 16 andadjacent end of camshaft 12. One component of such mechanism is a splineconnection 21 coupling the end of camshaft 12 to an annular axialprojection 22 of drive gear 16. Axial movement of camshaft 12 isprevented by a thrust washer 23 in bore 20 so that one effect of thespline connection 21 is to provide for axial movement of the drive gear16 relative to the camshaft and relative to gear 17.

The splines of connection 21 are helical so that any such axial movementof the drive gear 16 results in rotation of the camshaft 12 relative tothe drive gear. Thus if the axial position of the drive gear 16 isvaried in response to changes in engine speed, the desired advanc ingand retarding of timing can be effected.

Considering now the means for automatically varying the axial positionof drive gear 16 in response to changes in engine speed, a circularconcavity 24 in the side of drive gear 16 which faces away from camshaft12 is closed by a disc 26 secured to the rim of the concavity by anannular flexible diaphragm 27, the concavity, disc and diaphragm beingcentered on the rotary axis of the drive gear to define a vortex chambertherein as will hereinafter be discussed in more detail.

A rod 28 has a first end secured to the center of disc 26 by a nut 29and extends through an axial bore 31 in the drive gear 16 and into anaxial bore 32 in the adjacent end of the camshaft 12. Bore 31 of thedrive gear 16 has a diameter conforming to that of rod 28 while bore 32in the camshaft is of substantially greater diameter except for terminalportion 33 which is of reduced diameter to receive and pilot the end ofrod 28.

A compression spring 34 is disposed coaxially around rod 28 within thecamshaft bore 32 and bears against a flange 36 on the rod, with thefixed end of the spring being abutted against a lip 37 on a sleeve 38which is held in bore 32 by a snap ring 39. Spring 34 thus exerts aforce which tends to move the rod 28, and thus drive gear 16, towardscamshaft 12.

A similarly directed axial force on the drive gear 16 is generated, whenthe gear is being turned by gear 17, by the torque at the helicalsplines of connection 21. Inward movement of the drive gear 16 inresponse to these combined forces acts to shift camshaft 12 angularly insuch a manner as to retard the engine timing as hereinbefore described.

To create a normally counterbalancing axial force on the drive gear 16,rod 28 functions as a spool valve controlling a fluid pressure exertedagainst the drive gear. For this purpose, a section of the rod 28adjacent the inner end of drive gear bore 31 is of reduced diam terforming a flow passage 41 which coacts with control edge 42 of bore 31.Radially directed passages 43 in the drive gear 16 communicate bore 31with the vortex chamber 24 therein. Engine lubricating oil is admittedto camshaft bore 32 through a fitting 44 on housing section 19 andpassage 46 and apertures 47 in flange 36 of rod 28 transmit such oil tothe chamber 48 between drive gear 16 and the end of camshaft 12. Thepressure of such oil in chamber 48 acts against the adjacent surface 49of the drive gear 16 and tends to move the gear away from camshaft 12thereby tending to advance engine timing through the action of thehelical spline connection 21.

The amount of pressure which the oil in chamber 48 exerts against drivegear 16 is varied in response to engine speed changes through the spoolvalve action of the rod 28. In particular, oil continually flows intochamber 48, through passage 46 which has a flow restriction 51 and flowsout of the chamber past the control edge 42. From control edge 42 suchoil passes through bores.31 and 43 of the drive gear 16 into the vortexchamber 24 thereof and subsequently passes out of the vortex chamberinto housing 18 through apertures 52 in disc 26, the oil then beingreturned to the lubricating oil circulation system of the engine. Theoil flow past control edge 42,

and thus the oil pressure within chamber 48, varies in response to axialmovement of the control rod 28.

The axial position of rod 28 is turn responsive to engine speed inasmuchas the oil volume 53 within the vortex chamber 24 rotates with the drivegear 16 and is subjected to centrifugal force which generates pressuretending to force disc 26 and rod 28 outwardly away from camshaft 12against the action of spring 34.

Rod 28 is not affected by oil pressure other than that within vortexchamber 24 inasmuch as bores 31 and 33 are of equal diameter. In orderto avoid an accumulation of oil within bore 33 which would react againstthe rod 28, a drain passage 54 connects bore 33 with a fitting 56 onhousing section 19 to return any oil within bore 33 to the enginecirculation system. For similar reasons, a drain passage 57 connectsfitting 56 with the region of bore 20 adjacent the end of projection 22of drive gear 16.

In operation, drive gear 16 is urged inwardly towards camshaft 12 by theaction of spring 34 combined with the torque generated axial force ofhelical spline connection 21. Such forces are opposed by the oilpressure exerted against surface 49 of the drive gear 16. At constantengine speeds these opposed forces are balanced to maintain the drivegear 16 at a fixed axial position at which optimum engine timing isobtained. If engine speed increases, drive gear 16 turns more rapidlyincreasing the centrifugal force on the oil volume 53 within vortexchamber 24. Oil 53 then exerts a greater pressure against disc 26thereby unbalancing the forces acting on rod 28 and causing the rod tomove outwardly from camshaft 12. Such movement of rod 28 reduces theflow aperture past control edge 42 and therefore raises the oil pressurewithin chamber 48. The increased pressure within chamber 48 reactsagainst surface 49 moving the drive gear 16 outwardly and thus, throughthe action of the helical spline connection 21, advancing timing.

Upon a decrease in engine speed a reverse action occurs. Drive gear 16turns more slowly decreasing the centrifugally generated oil pressureagainst disc 26. Rod 28 is therefore drawn inwardly by spring 34 and thetorque produced axial force at connection 21, which increases the flowpassage past control edge 42 and lowers oil pressure Within chamber 48.Less outward pressure is then exerted against drive gear 16 with theresult that the gear also moves inwardly and retards the engine timing.

The angular adjustment of camshaft 12 by axial movement of drive gear 16does not require helical splines in connection 21 if the drive gearitself has helical teeth rather than being a spur gear as in theembodiment of FIGURE 1. Such adjustment is also accomplished if both thesplines of connection 21 and the teeth of gears 16 and 17 are helical.

Many modifications of the invention are possible. In the embodiment ofFIGURE 1, for example, the timing adjustment is determined by thecentrifugally generated oil pressure in vortex chamber 24. However theaxial movement of drive gear 16 to make the adjustment is effected bythe oil pressure in chamber 48 which in conjunction with the spool valveaction of rod 28 functions as a. form of hydraulic booster. By makingthe vortex chamber relatively larger, and making certain furthermodifications, it is possible to dispense with the hydraulic booster andto utilize the centrifugally generated oil pressure directly to move anelement to make the timing adjustment. The moving element need notnecessarily be the camshaft drive gear. The drive gear may be fixedagainst axial movement, for example, while arranging for a section ofthe camshaft itself to move axially in response to the oil pressurechanges. An embodiment of the invention employing both of thesemodifications is shown in FIGURE 2.

Referring now to FIGURE 2, there is shown one end of a camshaft 58 whichoperates a fuel injection system as in the embodiment of FIGURE 1. Ahelical spline connector 59 couples camshaft 58 to a camshaft extension61 which is coaxial therewith and journalled in an adapter member 62. Atthe side of adapter 62 opposite from camshaft 58 a drive gear 63 isdisposed coaxially on the camshaft extension 61 and engaged therewith bya second helical spline connection 64. Axial movement of the drive gear63 is prevented by a thrust washer 66 secured to adapter 62. Thus,through the action of the two helical spline connections 59 and 64,longitudinal movement of the cam shaft extension 61 will turn camshaft53 and effect timing adjustments in a manner analogous to that of themechanism of FIGURE 1.

The gear 63 is engaged with a gear 67 which forms part of the enginegear train and thus is coupled directly or indirectly, to the enginecrankshaft. Gears 63 and 67 are enclosed by a cover 68 secured toadapter 62 to form a closed gear housing in conjunction therewith.

Considering now the means by which axial movements of the camshaftextension 61 are effected to adjust timing, a vortex chamber is providedin drive gear 63 by a concavity 69 in the side of the gear which facesaway from adapter 62. Chamber 69 is closed by a circular plate 71secured at the side of the drive gear 63 and which supports acylindrical housing 72 that is coaxial with the gear and into which theouter end of camshaft extension 61 extends. A compression spring 73 isdisposed wihtin housing 72 between the end of camshaft extension 61 andthreaded spring tension adjustment 74 which projects from the end of thehousing. Spring 73 thus urges the camshaft extension 61 towards camshaft58 tending to retard timing through the action of the helical splineconnections 59 and 64.

To provide a counterbalancing axial force on the camshaft extension 61under steady operating conditions, a disc 76 is secured to the camshaftextension within vortex chamber 69 in coaxial relationship thereto. Disc76 has a diameter similar to that of the vortex chamber 69 and isslidable therein with the camshaft extension 61. Engine lubricating oil75 is admitted to the vortex chamber through a passage 77 in adapter 62which communicates with a groove 78 on camshaft extension 61. Groove 78in turn is communicated with the region between disc 76 and drive gear63 by a passage 79 extending Within the camshaft extension 61. Apertures81 in disc 76 and apertures 82 adjacent plate 71 provide for the escapeof such oil into the housing formed by adapter 62 and cover 68 fromwhich it may be returned to the engine lubricating system.

In operation, with the engine at a constant speed, the force exerted oncamshaft extension 61 by spring 73 is counterbalanced by the forceexerted against disc 76 by the centrifugally generated oil pressure inthe vortex chamber 69 and the timing remains fixed. Upon an increase inengine speed, the oil pressure against disc 76 increases moving camshaftextension 61 outwardly and advancing timing. Upon a decrease in enginespeed such oil pressure also decreases allowing spring 73 to force thecamshaft extension 61 inwardly and thereby retard timing.

Inasmuch as the centrifugally generated oil pressure in vortex chamber69 acts directly to move to the timing adjustment means in theembodiment of FIGURE 2, the vortex chamber is of greater diameter thanin the embodiment of FIGURE 1 in order to produce suflicient force.

What is claimed is:

1. An automatic timing adjustment mechanism for an engine of the classhaving a timing camshaft and a drive gear therefor as operative elementsof the engine timing system said camshaft and drive gear being coupledthrough axially movable means to vary the angular phase relationshiptherebetween and wherein said drive gear has an annular concavitytherein, comprising, in combination, means defining a vortex chamberwithin said concavity of said drive gear, a volume of liquid containedwithin said vortex chamber for centrifugally generating a fluid pressuretherein which is proportional to the speed of said engine, a resilientlymounted element Within said drive gear exposed to said fluid pressurefor said movement in response to changes thereof, and means transferringmotion of said resiliently mounted element to said axially movable meansfor adjusting said angular phase relationship in response to changes insaid engine speed.

2. An automatic timing adjustment mechanism as defined in claim 1wherein said liquid within said vortex chamber is oil derived from saidengine, and comprising the further combination of means forming passagesfor continually circulating said oil through said vortex chamber.

3. An automatic timing adjustment mechanism as defined in claim 1wherein said means transferring motion of said resiliently mountedelement to said axially movable means is a hydraulically operated forceamplifying means operated from the lubricating oil system of said engineand controlled by said resiliently mounted element.

4. An automatic timing adjustment mechanism as defined in claim 3wherein said drive gear is operativeiy engaged with an end of saidcamshaft and is movable axially relative there to to vary said angularphase relationship therebetween, said hydraulic force amplifying meansbeing situated between said drive gear and said end of said camshaft toexert said force therebetween.

5. An automatic timing adjustment mechanism for an engine of the classhaving first and second rotatable members as operative elements of theengine timing system, said first rotatable member being a drive gearcoupled to said second rotatable member and being movable in an axialdirection relative thereto to vary the angular phase relationshiptherebetween, means defining a vortex chamber which rotates with saidfirst and second members, said vortex chamber being situated within saiddrive gear, a volume of liquid contained within said vortex chamber forcentrifugally generating a fluid pressure therein which is proportionalto the speed of said engine, a resiliently mounted element exposed tosaid fluid pressure for movement in response to changes thereof, saidresiliently mounted element being a movable disc disposed within saiddrive gear and forming a wall of said chamber whereby said disc movesaxially in said gear in response to said changes of fiuid pressuretherein, means transferring motion of said resiliently mounted elementto said first rotatable member for adjusting said angular phaserelationship in response to changes in said engine speed, said motiontransferring means having a spool valve rod secured to said disc andextending into an enclosed region between said gear and said secondrotatable member and defining a fluid outlet for said region whichvaries in accordance with the axial position of said spool valve rod,and means for admitting fluid under pressure into said region wherebysaid fluid exerts an axial force on said drive gear which varies inaccordance with the axial position of said spool valve rod.

6. An automatic timing adjustment mechanism as defined in claim 1wherein at least a portion of said camshaft is movable in an axialdirection relative to said gear to vary said angular phase relationshiptherebetween, and wherein said resiliently mounted element comprises adisc disposed in said vortex chamber in said gear and forming a wall ofsaid chamber, said disc being coupled to said shaft whereby said shaftis shifted axially in response to said changes of fluid pressure in saidchamber.

References Cited UNITED STATES PATENTS LAURENCE M. GOODRIDGE, PrimaryExaminer.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,401 ,572September 17 1968 John M. Bailey It is certified that error appears inthe above identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 41, "roating" should read rotating Column 5, line 24,"wihtin" should read within Column 6, line 4, cancel "said", secondoccurrence; line 24, "there to" should read thereto Signed and sealedthis 17th day of February 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

I Commissioner of Patents Attesting Officer

